In conventional electrical engineering as well as in conventional electrical and electronic devices, the principle physical quantity of charge carriers employed is their electrical charge. The behavior of the charge carriers, such as electrons, holes, or other quasiparticle excitations, in these devices is mainly influenced by electrical fields, for instance by applying a voltage, or by a magnetic field, which interacts with moving charge carriers by virtue of the Lorentz force.
However, charge carriers often comprise further physical quantities which may be exploited in the framework of appropriate devices. Since such a further physical property of the charge carriers, apart from their electrical charge, may additionally be employed, a further degree of interaction with the charge carriers may be used for the design and construction of novel devices.
Such an additional physical quantity is the spin of charge carriers which is a quantum physical property of electrons, holes and other quasiparticle excitations.
However, to create devices exploiting spin-based physical effects, a source for at least partially spin-polarized currents or charge carriers, as well as a detector for detecting the spin state of charge carriers or a current of charge carriers, is needed to provide and/or to detect interactions with this physical quantity. Needless to say, such a source or a detector should also be compatible with the underlying technology.
While a wide range of metallic elements, compounds and materials exists, which may be utilized to provide or to detect an at least partially spin-polarized current, especially in the field of semiconductor technology, such a source for an at least spin-polarized current or an appropriate detector is still not satisfactorily implemented. In metallic systems, ferromagnetic metals, compounds, or elements such as iron (Fe), cobalt (Co), or nickel (Ni) may be used. However in semiconductor systems and devices this need is still not satisfied.